The availability of inexpensive CMOS technologies has created new opportunities for automated material handling within supply chain management. Especially, radio based identification has appeared in a variety of forms in the past decade, from keyless entry batch readers to automatic toll collection to Smartcards.
Radio frequency identification (RFID) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders. Today, a significant trust in RFID use is in enterprise supply chain management, improving the efficiency of inventory tracking and management. Passive RFID tags have no internal power supply. The electrical current induced in the RFID tag antenna by incoming radio frequency waves provides enough power for the CMOS integrated circuit in the tag to power up and transmit a response. However, often it is necessary to provide together with the RFID tag a possibility to easily enable a user of the RFID tag to check the functionality of said tag for example due to security purposes. See also “Bringing UHF RFID tags into mainstream supply chain applications”, by Rob Glidden and John Schroeter, on the rfdesign.com web site in July of 2005.
Assuming for example the scenario that a customer wants to buy a product which is secured by an RFID tag, after having paid for the product at the cash desk, he wants to be sure that the RFID tag has been disabled so he can leave the shop without activating an alarm system just because the RFID tag was accidentally not deactivated by the cashier. One possibility to solve this problem is to install additional RFID check terminals, which enable a customer to check the functionality and activity of an RFID tag just for example before leaving a shop. However, this is rather inconvenient for a customer and also creates additional costs for installing such terminals.
“Clipped RFID Tags Protect Consumer's Privacy” by Guenter Karjoth and Paul Moskowitz, in ERCIM News, January 2007, shows an RFID tag at which consumers can physically separate a part of the tag antenna from the tag. Such separation provides visual confirmation that the tag has been turned into a proximity tag.
In a different context, in “A controlled-release microchip” by John T. Santini Jr. at al., in Nature, Vol. 397, 28 Jan. 1999, a solid-state silicon microchip is reported that can provide controlled release of single or multiple chemical substances on demand which release mechanism is based on the electrochemical dissolution of thin anode membranes covering micro-reservoirs filled with chemicals in solid, liquid or gel form.
Another possibility is to attach special display elements directly to the RFID tag which enable a user of the RFID tag to visually directly check the functionality of the RFID tag. However, since passive RFID tags have no internal power supply and the incoming radio frequency waves which are picked up by the integrated antenna provide just enough power for the CMOS integrated circuit to power up and transmit a response, additional power supplies and special RFID tag readout electronics have to be supplied together with the RFID tag. This may be a solution for extremely expensive goods but not for RFID tags which are attached to low cost mass produced goods.
Therefore, there is a need for a visual display which is cheap and compatible with mass fabrication techniques.